The invention relates to a light source having a luminescent layer, whose light is guided through an optical filter.
Such a light source for use in a colour projection arrangement with three monochromatic cathodoluminescence light sources is known from DE-OS 38 36 955.
A multilayer interference filter, which concentrates the light radiation in the forward direction as a light collection filter, is arranged between a front substrate and a layer of luminescent material. Interference filters are difficult to manufacture. A significant problem is that the thickness of the individual layers should be maintained constant, which is an absolute requirement for a satisfactory operation.